This invention relates to an improved process for the removal of solids of varying sizes from liquid. A particular aspect of the invention relates to the removal of sand from liquid-tar sand slurry in a process for recovery of oil from tar sands.
The removal of solid particles of varying sizes from liquid often requires an expensive and sophisticated process partially because the particles of one size range interfere with the removal of particles of another size range. For example, coarse particles can be removed by passing the liquid containing solid particles through a filtration zone; however, smaller particles tend to accumulate in the filtering zone, restricting the flow of rate and eventually plugging the passageway altogether. Similarily, when fine particles are sought to be removed by passing the liquid through a centrifuge zone the coarse particles' weight and bulk interfere with the process and increase the necessary size of the equipment. The present invention in its broad aspect obviates some of the problems inherent in the removal of solid particles of varying sizes from liquid.
Of particular interest is the application of the present invention to the removal of sand particles from a liquid slurry in a process for the production of oil from tar sands.
Tar sands, also known as oil or bituminous sands, are sands that are heavily impregnated or saturated with oil. Deposits of these sands are found in many areas of the world including Alberta, Canada, Utah and California. Although tar sands provide potentially attractive source of petroleum products, the recovery of valuable components from tar sands in an efficient and economical manner has been a problem. One process for recovery of oil from tar sands disclosed for example in U.S. Pat. No. 2,772,209 and U.S. Pat. No. 3,342,105 comprises adding a diluent to tar sand to form a slurry. The slurry is then heated or introduced into a cyclone as disclosed in U.S. Pat. No. 2,910,424 to achieve separation of oil. One problem encountered by these processes is that tar sand has a high percentage of inorganic solids. The solid particles are of different size ranges so that a complete separation of solids necessitates the use of sophisticated, expensive and energy consuming devices such as centrifuges. A substantially complete removal of solids in a filter zone is impractical because smaller size particles accumulate on the filter restricting the flow rate and resulting in plugging the filter. The expense associated with substantially complete removal of solid particles leads to compromizes in the level the solid removed which in turn results in production of oil having high ash content and therefore not suitable for some applications.
In its particular aspect, this invention obviates some problems encountered in processes for the recovery of oil from tar sands.
Thus, one object of the invention is to provide a process for an efficient removal of solid particles of varying sizes from liquid or from a liquid slurry.
Another object of the invention is to reduce the size and the cost of equipment necessary for the removal of solid particles of varied sizes from a liquid.
Still another object of the invention is to provide a process for recovery of oil from tar sand, which is efficient and results in production of oil having a low ash content.
Still another object of the invention is to provide a process for an efficient and inexpensive removal of solid particles from tar sand slurry.
A still further object of the invention is to utilize fine sand particles contained in tar sand for the production of coke.
Still another object of the invention is to provide a process for production of oil having low ash content from tar sands which eliminates the need for the expensive removal of fine sand from the liquid.
A still further object of the invention is to provide a process for removal of oil from tar sands which does not use water for formation of tar sand slurry, thereby eliminating problems associated with sludge and oil-water emulsion separations.
Still another object of the invention is to provide a method for production of low ash content coke as a by-product in the process for recovery of oil from tar sands.
Other objects of the invention will become apparent to those skilled in the art upon studying this disclosure.